75245-71-5Relevant articles and documents
Synthesis and reactivity of benzylic and allylic samarium compounds
Bied,Collin,Kagan
, p. 3877 - 3890 (2007/10/02)
Benzyl and allyl samarium species are prepared by reaction of benzylic or allylic chlorides with SmCp2. They present a wide scope of reactivity towards aldehydes, ketones and acid chlorides.
Reactions of Carbonyl Compounds with Grignard Reagents in the Presence of Cerium Chloride
Imamoto, Tsuneo,Takiyama, Noboyuki,Nakamura, Kimikazu,Hatajima, Toshihiko,Kamiya, Yasuo
, p. 4392 - 4398 (2007/10/02)
The addition of Grignard reagents to ketones is significantly enhanced by cerium chloride with remarkable supression of side reactions, particularly enolization.Some esters, which are prone to side reactions, also react readily with Grignard reagents in the presence of cerium chloride to give normal reaction products in reasonable to high yields.
ORGANOCERIUM REAGENTS. NUCLEOPHILIC ADDITION TO EASILY ENOLIZABLE KETONES
Imamato, Tsuneo,Sugiura, Yasushi,Takiyama, Nobuyuki
, p. 4233 - 4236 (2007/10/02)
Organocerium reagens, prepared from organolithiums and anhydrous cerium (III) chloride, react cleanly with easily enolizable ketones to afford the addition products in good to excellent yields.
Carbon-Carbon Bond-Forming Reactions Using Cerium Metal or Organocerium(III) Reagents
Imamoto, Tsuneo,Kusumoto, Tetsuo,Tawarayama, Yoshinori,Sugiura, Yasushi,Mita, Takeshi,et al.
, p. 3904 - 3912 (2007/10/02)
Carbon-carbon bond-forming reactions using cerium metal or organocerium(III) reagents have been investigated.Cerium amalgam is an effective reagent for the chemoselective preparation of homoallylic alcohols from allyl halides and carbonyl compounds.These same reagent can also be satisfactorily employed for the Reformatsky-type reaction of α-halo esters with carbonyl compounds.It has been shown that organocerium(III) reagents are conveniently generated by the reaction of organolithiums with cerium(III)iodide or cerium(III)chloride.The reagents are less basic thanorganolithiums or Grignard reagents, and they react cleanly at -78 to -65 deg C with various carbonyl compounds to afford the addition products in high yields, even though the substrates are susceptible to enolization or metal-halogen exchange with simple organolithiums.The same reagents react also with α,β-unsaturated compounds to yield 1,2-addition products in high selectivity.
Conformations and Rotational Barriers of 1,3-Diphenylallyllithium Compounds
Boche, Gernot,Buckl, Klaus,Martens, Diether,Schneider, Dieter R.
, p. 1135 - 1171 (2007/10/02)
The phenyl substituents of the 1,3-diphenylallyl anions 10 (gegenion lithium, solvent tetrahydrofuran) can exist in the exo,exo-, endo,exo- and/or endo,endo-conformations.We have investigated the influence of substituents R at C2 on the equilibria of these solvent separated ion pairs.While 10a (R = H) is the only one to exist predominantly in the exo,exo-conformation, and in 10b and c (R = CH3 and CN, respectively) the endo,exo-conformers predominate, in 10d, e and f (R = C2H5, C6H5 and iPr, respectively) there is increasing preference for the endo,endo-conformation, which in 10g (R = tBu) is the dominant (>/= 95percent) conformation.A vast congestion in the endo,endo-conformation is avoided by a rotation of the phenyl rings out of the plane of the allyl carbon atoms, and an expansion of the sp2 angles in the allyl moiety.The rotational barriers around the allyl anion bonds decrease from 19.1 kcal*mol-1 (10a) to 12.5 kcal*mol-1 (10f).Since this trend parallels to the above mentioned shift of the equilibria, it is due to ground state effects.The rotational barriers are only slightly (10a,b) if at all influenced by gegenion effects, which is in sharp contrast to the parent allyl "anion".Therefore, the rotational barriers of the allyl anions 10 are qualified for a comparison with the corresponding radicals and cations.Furthermore, with ΔG(excit)273 deg C = 19.1 kcal*mol-1 as a lower limit value for the rotational barrier of the parent allyl anion, one can estimate that the true value of this species must be close to barriers calculated with STO-3G and 4-3l-G programs (ca. 26 kcal*mol-1).
